Induction-motor control.



F. E. CASE. INDUCTION MOTOR CONTROL. APPLICATION FILED JULY 8,1908.

Patented Apr. 27, 1909.

:4 WITNESS/F5. MSZEAZTUE W v FEAJVK L. CASE.

Sim/66w by-step as the motor accelerates.

' UNITED STATES PATENT OFFICE.

FRANK E. CASE, OF SGHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY,

" A CORPORATION OF NEW YORIC.

INDUCTION-MOTOR CONTROL.

Spec'ificationot Letters Patent.

Patented April 27, 1909.

Application filed July 8, 190a. Serial No. 442,454.

To all "whom it may concern: I

Be it known that I, FRANK E. CASE, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Induction-Motor Control, of which the following is a specifica tion.

My invention relates to the control ofinduction motors, and its object is to increase the number of accelerating connections or resistance steps obtainable with a given number of resistance sections with a com paratively slight increase in the amount of controlling apparatus. Induction motors are customarily provided witlureslstances in the secondary circui which are arranged to be cut out step- If a large number of resistance steps are desired, the number of resistance connections and switch contacts for controlling them becomes large.

My invention consists in the addition of impedances in the primary circuit, with short-circuiting switches arranged to cut the primary impedances into and out of circuit, as the several sections of the secondary imedances are short-'circuited. Thus, ;by. a comparatively small addition to the amount of control-apparatus, I am enabled to double the number of resistance steps.

My invention will best be understood by reference to the accompanying drawing, which shows diagrammaticall an induction motor provided with contro ingmeans arranged in accordance with my invention;

In the drawing, A represents the primary and B the secondary of an induction motor. The secondary member is provided with collector rings O. The primary winding is shown supplied with three-phase current through step-down transformers D. Impedances E are inserted in the primary leads, and these may be either inductive or noninductive.

F represents impedances in the circuit of the secondary member of the motor, which are arranged to be short-circuited step-byste (E represents electromagnetically actuated switches for short-clrcuitmg the primary 11npedances E.

'ondary impedah'ces F.

H, H and H re resent electromagnetically-actuated switc ies for short-circuiting. different sections of the secondary impedances F.

i K, K, K represent electromagnetically actuated switches for closing the primary circuit of the motor.

J represents a controlling switch for controlling the actuating windings of the electromagnetically-actuated switches. This switch J is shown diagrammatically,with its contents developed on a plane surface, and with seven operative positions in addition to its off-position.

.With switch J in the off-position, the 'primary circuit is open but the secondary circuit is complete with all the secondary impedances in circuit. When switch J is moved to its first position, the e'lectromagnetically-actuated switches or contactors K are ener ized, which complete the primary circuit t rough theimpedances E. When switch J ismoved to its second position, the primary impedances E are short-circuited by means of contactors G. In the third position the contactors G are deenergized, and contactors Hare energized. This cuts the primary impedances back into circuit and short-circuits one section of each of the sec- In moving to its fourth position, switch J maintains the contactors H energized, While reenergizing contactors G. Thus, the primary impedances are again short-circuited. In its fifth position, contactors G are denergized, while contactors H are energized, thereby shortcircuiting another section of the secondary impedances while cutting the primary impedances again into circuit. This cycle of operations is repeated through the further positions of switch J, the primary impedances being cut into and out of circuit, as each section of the secondary impedances is shortcircuited. In the last position of switch J, all the impedances are short-circuited.

It will be understood that my invention permits of many modifications, as, for instance, altering the connections of the secondary resistances, so as to obtain a greater number of resistance steps. Accordingly, I do not desire to limit myself to the particular connections and arrangement of parts here shown, but aim in th'e a ppended claims to cover all modifications which are within the scope of my invention.

7 What I claim asneW and desire to secure by Letters Patent of the United States, is,

1; In combination Withan induction mo tor, impedances in series with the primary of the motor, impedances in series with'the secondary, switch contacts for short-circuiting tor, means for decreasing the impedance of the primary circuit of the motor, means for decreasing the secondary 1mpedance* radu-'- ally, and controlling means whereby t e impedance of the'primary circuit is alternately increased and decreased as theimpedance of the secondary circuit is gradually decreased.

3. In combination with an induction motor, impedances in series with the primary and secondary of the motor respectively,

switch contacts for sho'rt-circuiting the primary lmpedances; switches for short cn'culting the secondary impedances step-by-step,-

and controlling means arranged to open and close the first named contacts alternatelyas the last-named contacts are, successively closed. p

4. In combination with an induction motor, impedanccs in series with the primary and secondary-of the motor respectively, electromagnetically-actuated switches for short-circuiting the primary impedances, electromagneticallyactuated switches for short-circuiting the secondary iinpedances step-by-step, and awcontrollin'g switch arranged to energize and denergize the actuatmg windings of the inst-named e/WIEC'llCS alternately as the actuating windings of the last-named switches are successirelv-energized.

In witness whereof, I have hereunto set my hand this 3d day of July, 1908.

. FRANK E. CASE.

Witnesses:

BENJAMIN -B. HULL, I HELEN ORFORD. 

